The role of specific dietary factors in cancer prevention has been assessed through epidemiologic studies and animal experiments. For many of these agents, information is incomplete concerning their quality and form in the food supply, bioavailability, biochemical effects and the interaction with other nutrients. To further define these parameters in the human population, a cooperative research effort between the Beltsville Human Nutrition Research Center (BHNRC) and the Cancer Prevention Studies Branch, DRCCA, will be conducted. The three-year interagency agreement will encompass the development of analytical methods for routine analysis of nutrients as well as further investigation of the pharmacodynamics and interactions of those dietary factors identified as possible cancer preventive agents. The overall goal is to obtain further information on those factors identified as potential cancer preventive agents with respect to their quantity and bioavailability in the food supply, health effects of supplementation and their pharmacokinetics in a healthy population, as well as improving methods for analysis of these nutrients. Investigations of the trace element selenium (Se) will be done during the first year. To date, few supplemental studies have been done and many questions concerning the pharmacokinetics and bioavailability of Se in its organic and inorganic forms remain unanswered. In addition, most of these studies have been done in populations with low Se status and, therefore, results cannot be extrapolated to the U.S. population which appears to have adequate se status. The initial phase of the Se studies will examine the pharmacokenetics of a single oral dose of selenite and selenomethionine in a healthy population who have adequate Se intake at baseline. The second phase will examine the bioavailability and health effects of multiple doses of inorganic and organic selenium. Following these, a study will be done correlating dietary intake of B-carotene with B-carotene levels, retinol and retinol-binding protein levels in the blood. Further studies will examine interactions of dietary fat and fiber intake on vitamin and mineral balance.